1. Field of the Invention
The present invention relates to a photographing apparatus having an autofocus function, a method of calculating information for focus control, and a camera system.
2. Description of the Related Art
In recent years, many of portable apparatuses (photographing apparatuses) with photographing functions have autofocus functions. In the photographing apparatuses of this type, there is an apparatus in which an image pickup device having pixels for focus detection (hereinafter referred to as “AF pixels”) incorporated therein in addition to pixels for image pickup (normal pixels) to form an image is adopted and autofocusing is performed by a pupil division phase difference method. In this method, it is necessary to divide a pupil in right and left directions and to form AF pixels having image pickup portions that receive luminous fluxes passed through the right and left pupils separately, in the image pickup device. High-speed autofocusing is possible by generating an AF signal for focusing by an arithmetic operation on image signals by the AF pixels of these types (hereinafter referred to as “AF operation” or “correlation operation”), and performing the focusing.
In the AF operation in which a displacement amount of the focusing (a defocus amount) is obtained in accordance with a state of use of a lens, an arithmetic operation using an interval between a plurality of images by different luminous fluxes on a light receiving surface (two-image interval) and various parameters for the AF operation (hereinafter referred to as “AF operation parameters”) is performed.